1. Field of the Invention
The present invention relates to a semiconductor device and a method of fabricating the same, and more particularly, to a device having a damascene type Cu line protected by a HfOx layer and method of forming the same.
2. Discussion of the Related Art
Generally, Cu lines for metal wiring in semiconductor devices cannot be formed by RIE (reactive ion etching), unlike the popular aluminum metal lines. Such Cu lines are generally formed by the damascene method by designing a line layout, filling a via hole and trench with Cu, and planarizing the Cu. In doing so, SiN is typically deposited on a surface of the exposed Cu line after planarization, to be used as a diffusion barrier and etch stop layer. Hence, the surface of the final Cu line interfaces with SiN.
FIGS. 1A to 1C are cross-sectional diagrams for explaining a conventional method of forming a Cu line.
FIG. 1A shows a cross-sectional view of a Cu wire after completion of damascene and planarization processes. Referring to FIG. 1A, an insulating layer 11 is deposited on a substrate 10 provided with a prescribed device. Trenches and vias (not shown) are formed by a damascene process. The trench is filled with Cu, and the Cu is planarized to complete a Cu line 12.
FIG. 1B shows a cross-sectional view of a protective layer of SiN 13 deposited on the Cu line 12. Referring to FIG. 1B, after completion of damascene and planarization processes, a protective layer 13 is formed by depositing SiN 13 on the Cu line 12.
FIG. 1C shows a magnified cross-sectional view of a part-A in FIG. 1B for explaining a problem occurring at a Cu—SiN interface.
Referring to FIG. 1C, Cu oxide 14 is formed on a surface of the Cu line 12 after completion of planarizing the Cu line 12. Specifically, the Cu oxide 14 may be formed in the planarization process and in the subsequent transfer of the substrate to other equipment for SiN deposition after completion of the planarization process. However, the Cu oxide formed on the Cu line brings about various reliability problems in many processes. The substantial problems are explained as follows.
First of all, Cu oxide may degrade adhesion between SiN 13 and Cu 12. Cu oxide 14 between SiN 13 and Cu 12 makes the corresponding interface more unstable.
Secondly, different from Al oxide, the oxygen in Cu oxide 14 tends to migrate along Cu surfaces, thereby leading to corrosion of the Cu line 12 and any metal lines in physical contact therewith.
Thirdly, Cu oxide 14 may play a role as a negative electrode in galvanic corrosion.
Fourthly, the unstable interface between Cu 12 and SiN 13 due to the Cu oxide 14 accelerates interfacial diffusion of surface atoms that are most vulnerable to electro-migration (hereinafter abbreviated EM), leading to accelerated formation of voids.
Finally, the unstable interface causes unstable adhesion, whereby hillocks can be easily formed at the interface.